Magnesium-lithium alloys in metal matrix composites — A preliminary report

Abstract

Procedures are described for the fabrication of fibrous composites based on magnesiumlithium alloys as a matrix. Such composites have been produced containing planar random and aligned (continuous and discontinuous) fibres of carbon, alumina and silicon carbide. For all of these, except silicon carbide whiskers, significant fibre degradation occurred, during fabrication or subsequent heat treatments, either by chemical reaction or by grain boundary penetration of lithium. Further consequences of the high atomic mobility exhibited by the matrix are manifest in the mechanical behaviour of the composites. Although considerable property enhancement is possible by fibre reinforcement, a significant diffusional contribution to the stress relaxation mechanisms results in a dependence of work hardening rate and failure strain on temperature and strain rate, even around room temperature and at relatively high strain rates. It is concluded that, although the system presents many practical difficulties, it is worthy of further study.